20062007 Plant Anatomy Basic plant anatomy 1 root root tip root hairs Roots Roots anchor plant in soil absorb minerals amp water amp store food fibrous roots 1 mat of thin roots that spread out ID: 768436
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2006-2007 Plant Anatomy
Basic plant anatomy 1 rootroot tiproot hairs
Roots Roots anchor plant in soil, absorb minerals & water, & store foodfibrous roots (1)mat of thin roots that spread outmonocotstap roots (2) 1 large vertical root also produces many small lateral, or branch roots dicotsroot hairs (3)increase absorptive surface area 2 1 3
Basic plant anatomy 2 rootfungi at tips of the roots Mycorrhizae-Symbiotic relationshipshoot (stem) budsterminal or apical buds-located at the topaxillary buds-located at the V formed b/t leaf and stem
Modified shootsstolons (strawberries) rhizome (ginger) tuber (potato) bulb (onion)
LeavesFunction of leavesphotosynthesisenergy productionCHO productiongas exchangetranspiration simple vs. compound
Putting it all together Obtaining raw materialssunlightleaves = solar collectorsCO2stomates = gas exchange H2Ouptake from rootsnutrients uptake from roots
Plant TISSUESDermalepidermis (“skin” of plant)single layer of tightly packed cells that covers & protects plant Groundbulk of plant tissue photosynthetic mesophyll, storage Vasculartransport system in shoots & roots xylem & phloem
Plant CELL types in plant tissuesParenchyma“typical” plant cells = least specializedphotosynthetic cells, storage cellstissue of leaves, stem, fruit, storage rootsCollenchymaunevenly thickened primary wallssupportSclerenchyma very thick, “woody” secondary wallssupport rigid cells that can’t elongatedead at functional maturity If I ’d only had triplets !
Xylem and PhloemXylem- water conducting cells. xylem vessels- found mostly in angiosperms have pits for water movement. xylem tracheids- long thin cells strengthen with lignin
tracheids vessel elements Vascular tissue Aaaah … Structure – Function again ! vessel element dead cells Xylem move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H 2 O transpirational pull
Phloem: food-conducting cellscarry sugars & nutrients throughout plant sieve tube companion cell living cells plasmodesmata sieve plate
Phloem: food-conducting cellssieve tube elements & companion cells
PhloemLiving cells at functional maturitycell membrane, cytoplasmcontrol of diffusionlose their nucleus, ribosomes & vacuolemore room for specialized transport of liquid food (sucrose)Cells sieve tubessieve plates — end walls — have pores to facilitate flow of fluid between cellscompanion cellsnucleated cells connected to the sieve-tube help sieve tubes Aaaah … Structure–Function again !
2006-2007 Plant Growth
Life Cycle of PlantsAnnuals- in one year Ex:Wildflowers, cropsBiennials- completed in 2 years Ex: radishes and carrotsPerennials- continues for many years Ex. Trees
Growth in Plants Specific regions of growth: meristemsstem cells: perpetually embryonic tissueregenerate new cellsapical shoot meristemgrowth in length primary growthapical root meristemgrowth in lengthprimary growthlateral meristemgrowth in girth secondary growth
Apical meristemsshoot root
Root structure & growth protecting the meristem
Shoot growth Young leaf primordium Apical meristem Older leaf primordium Lateral bud primordium Vascular tissue protecting the meristem
Woody plants grow in height from tipprimary growthapical meristemWoody plants grow in diameter from sidessecondary growthlateral meristems vascular cambiummakes 2° phloem & 2° xylemcork cambiummakes barkGrowth in woody plants Primary phloem Primary xylem Secondary phloem Secondary xylem Annual growth layers Lateral meristems Primary xylem Primary phloem Bark Epidermis
Vascular cambiumlast year’s xylem early latephloem bark Phloem produced to the outside Xylem produced to the inside cork cambium vascular cambium xylem Why are early & late growth different?
Woody stemcork cambium vascular cambium xylem early late phloem bark How old is this tree? 1 2 3
Secondary Growth produced by the vascular cambium Vascular cambium Growth Secondary xylem After one year of growth After two years of growth Secondary phloem Vascular cambium X X X X X X P P P P C C C C C C C C C C C C C
Plant hormones auxingibberellinsabscisic acidethyleneand more…
Auxin (IAA)Effectscontrols cell division & differentiation phototropismgrowth towards lightasymmetrical distribution of auxincells on darker side elongate faster than cells on brighter sideapical dominance
GibberellinsFamily of hormonesover 100 different gibberellins identifiedEffectsstem elongationfruit growthseed germination plump grapes in grocery stores have been treated with gibberellin hormones while on the vine
Abscisic acid (ABA)Effectsslows growthseed dormancyhigh concentrations of abscisic acid germination only after ABA is inactivated or leeched outsurvival value: seed will germinate only under optimal conditionslight, temperature, moisture
EthyleneHormone gas released by plant cellsEffectsfruit ripening leaf drop like in Autumn apoptosis One bad apple spoils the whole bunch …
Fruit ripeningAdaptationhard, tart fruit protects developing seed from herbivoresripe, sweet, soft fruit attracts animals to disperse seedMechanismtriggers ripening processbreakdown of cell wallsofteningconversion of starch to sugarsweeteningpositive feedback systemethylene triggers ripening ripening stimulates more ethylene production
Apoptosis in plantsWhat is the evolutionary advantage of loss of leaves in autumn?Many events in plants involve apoptosis response to hormonesethyleneauxindeath of annual plant after floweringsenescencedifferentiation of xylem vesselsloss of cytoplasm shedding of autumn leaves
2006-2007 Don’t take this lying down… Ask Questions!!